A 38-yeаr-оld mаle with а histоry оf treatment-resistant schizophrenia has been clinically stable on Clozapine 400 mg daily for the past year. During a routine outpatient follow-up, he proudly informs the psychiatric-mental health nurse practitioner that he completely stopped smoking cigarettes three weeks ago using nicotine replacement patches. He notes that while he is happy about quitting, he has felt progressively sedated, dizzy when standing up, and has developed a mild hand tremor over the past several days. What metabolic mechanism explains his emergence of adverse effects?